From having been to both Upper and Lower multiple times in the past 3 years or so, I thought I'd give my input too.
For lower Antelope, I think there are good reasons to use a tripod. Yes, it can slow you down, but I prefer greater DOF and lower ISO's in case I need to play with shadows (if you include the sky in shots looking up, the skies may be blown out, or the canyon walls underexposed). I also tend to bracket in there. The other little difference with the photography tours vs. 'normal' tours is that when I've done it, I've always been allowed to go into the canyon immediately, whether it was just me alone or when I've gone with photographer friends. On the normal tours, you go as a group at intervals. I'm not sure but I'd suspect the group may tend to push you along at times if you're trying to work a certain area, or hold you back if you want to move ahead.
If you have two cameras, bring them in order to avoid/minimize lens changes; it's dusty in there! Keep your head on a swivel and keep looking behind you as you walk through the canyons.
LOLID said:
You can drive yourself to Lower and pay the entrance fee on site, but you cannot drive to Upper. For Upper you need to make a reservation with the Navajo affiliated tour companies. I used Overland Canyon and was pleased with them.
Well for clarification, at Upper Antelope you can drive up to the gate to join an on-site tour, as they do run their own 'on site' tours. You'll park your car inside and jump on one of their trucks.
Another thing I haven't seen mentioned yet; Upper Antelope is insanely crowded in the spring/summer when the beams are going. The main differences between the regular and photography tours show up then, as the photography tours do a good job of trying to get groups to the better locations to see the beams, yelling at the non-photography groups and holding them back at times so the photographers can get a shot. I've seen regular groups get rushed through such spots. Of course, some people are rude and will ignore everyone yelling at them so they can take their stupid selfies, but that can't really be helped if the tour guides aren't willing to physically step in. Oh, and the guides will throw dust up in the air so the beams show up better, while joking about killing your cameras...so hopefully your camera is weather sealed; even so, I'd seriously some additional home-made protection, like ziplock bags & rubber bands. I may look silly, but I've heard of lots of people having problems with their cameras after visiting.
I'm not 100% sure about Upper, but I do not believe you can join the photography tours at either canyon without having a tripod. I think I've been checked at both locations every time.
I prefer large cameras, but I must admit that the small EOS-M is a wonder ... Since the stones do not move very fast. 
